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03-30-2026, 10:48 AM
Hi Guys
The universal mains PT should be equivalent to the original 117V PT as far as the secondary windings go.
It is a wonder that a fan was used in the 80W and 160W bass amps since neither really warranted it.
If you want to add a fan, do it the modern way. Get the largest 12Vdc fan you can fit into the space, positioning it so that it pushes air past the output tubes and towards the rear. Use a 4-diode bridge running from the 6Vac to generate about 8Vdc with a 10,000uF filter cap. This operates the fan at slow speed and it will be inaudible in front of the amp.
In tube amps (other than Vox or VHT) one does not need massive air flow; instead, just to bias the airflow in the right direction.
Have fun
The universal mains PT should be equivalent to the original 117V PT as far as the secondary windings go.
It is a wonder that a fan was used in the 80W and 160W bass amps since neither really warranted it.
If you want to add a fan, do it the modern way. Get the largest 12Vdc fan you can fit into the space, positioning it so that it pushes air past the output tubes and towards the rear. Use a 4-diode bridge running from the 6Vac to generate about 8Vdc with a 10,000uF filter cap. This operates the fan at slow speed and it will be inaudible in front of the amp.
In tube amps (other than Vox or VHT) one does not need massive air flow; instead, just to bias the airflow in the right direction.
Have fun
